The conventional use of single-agent dietary approaches to prevent breast cancer (BC) can have limitations in that these compounds may not be sufficiently efficacious when acting alone to reliably prevent BC or they may require impractical or unsafe levels of consumption to acquire significant efficacy. A solution to this challenge is combinatorial approaches allowing reduced doses of the individual natural compounds that, in combination, render greater efficacy. We have shown that combined green tea polyphenols (GTPs) and sulforaphane (SFN)-enriched broccoli sprouts (BSp) administered at safe levels consumable by humans are highly effective in preventing BC tumors in mice that spontaneously develop BC. Our results indicate that the efficacy of this combinatorial dietary approach of GTPs and BSp depends on the ability of these natural dietary products to significantly impact epigenetic gene regulation. We hypothesize that combined GTPs and BSp are highly effective in neutralizing epigenetic aberrations of key tumor-related genes in BC as well as epigenomic alterations and that this combinatorial dietary approach allows less consumption of these dietary products to render a greater impact in preventing BC. These investigations are important for a number of reasons. First, it is important to elucidate the impac and mechanisms of this combinatorial dietary epigenetic approach and its effects on the epigenetics of key tumor-related genes since little is known about the combined epigenetic effects of these dietary products. Second, it is also important because we do not yet know the global profile of the epigenetic effects of these compounds and what other genes may be impacted by these compounds. Third, we do not yet fully understand what impact the combination of these compounds will have on BC tumors of different origins and pathways of carcinogenesis. Finally, there are few options for women who develop estrogen receptor-negative [ER(-)] BC and we have found that combined GTPs and BSp is highly effective in converting ER(-) tumors to ER(+) tumors that can be readily prevented with tamoxifen (TAM). It will therefore be important to more fully understand the mechanisms and efficacy of these combinatorial approaches in preventing ER(-) BC. A goal of this proposal is to confront these challenges through the use of novel techniques we have invented such as chromatin immunoprecipitation (ChIP)-genomic bisulfite sequencing (GBS) or ChIP-GBS and advanced epigenomic technologies. The impact of this proposed investigation will be significant since hundreds of thousands of women worldwide are affected by BC. The use of safe and effective combinations of epigenetic aberration-neutralizing dietary compounds has high translational potential for preventing BC by providing lower doses of these compounds, enhanced efficacy and greater cost effectiveness. There is also a need for identification of epigenetic biomarkers of BC that will aid in the predisposition, diagnosis and prognosis of BC. Finally, the proposed study will provide hope for women who are at high risk of developing highly lethal ER(-) BC and who have few options.